The researchers, which also include those from the UK and Germany, tested the egg-rejection behaviour of 18 species of Australian birds and 23 European ones.

In the Australian part of the study they placed bright blue plastic model eggs in nests to see if the host bird would eject, damage or abandon the odd coloured egg.

Langmore says light and visibility in the nest appeared to be the major factors in determining whether or not a host bird rejects a foreign egg.

"Hosts which built a small dark dome-shaped or cupped-shaped nest accepted the odd eggs but hosts with nests that had lots of light were able to discriminate between eggs and had higher rejection rates," she says.

Langmore says the findings suggest some hosts accepted cuckoo eggs rather than risk rejecting their own.

She says smaller hosts built smaller, closed nests that had a defensive advantage, as larger cuckoos could not enter to lay eggs.

"But it also makes it harder to spot the cuckoo egg because the nest is darker and they may not want to risk rejecting their own egg by mistake."

Langmore says previous studies suggest some host birds accept cuckoo eggs because the cost of keeping them is "low".

"Life history theory says some hosts may have time to re-nest and have more chicks; the energy used to raise a small cuckoo chick might not be high; or they may only have a small clutch of eggs," she says.

"But what we found was life history traits were not important at all."

She says the native Australian superb fairy wren was a good example of a bird that could not distinguish between its own eggs and cuckoo eggs so did not reject foreign eggs.

But it was also the only cuckoo host in the world that could identify impostor chicks in its nest and abandon them, says Langmore.

"It appears they lost the evolutionary arms race at the egg stage but instead of giving up, the arms race has escalated and the superb fairy wren has evolved to recognise cuckoo chicks."